1. Field of the Invention
The present invention relates to fabricating semiconductor devices and, more particularly, to a method for generating trace data reports in a fault detection system.
2. Description of the Related Art
Semiconductor devices, or microchips, are manufactured from wafers of a substrate material. Layers of materials are added, removed, and/or treated during fabrication to create the integrated, electrical circuits that make up the device. The fabrication essentially comprises four operations known as layering, patterning, doping, and heat treatment that can combined in hundreds of different ways, depending upon the particular fabrication process. See, e.g., Peter Van Zant, Microchip Fabrication A Practical Guide to Semiconductor Processing (3d Ed. 1997 McGraw-Hill Companies, Inc.) (ISBN 0-07-067250-4). The fabrication process generally involves processing a number of wafers through a series of fabrication tools. Each fabrication tool performs one or more of the four basic operations. The four basic operations are performed in accordance with an overall process to finally produce wafers from which the semiconductor devices are obtained.
One important aspect of the manufacturing process is process control. In particular, the fabrication tools and the fabrication environment must be controlled to achieve a satisfactory process. Certain operational parameters may be monitored and, when desired, the tool's operation can be altered to improve the process to yield more or better wafers.
Competitiveness in the semiconductor manufacturing industry is driven by increasingly complex product and process technologies and global competitive pressures on manufacturers to improve cycle time, quality, and process flexibility. Requirements for sub-quarter-micron device manufacturing and advanced batch control technologies are increasingly important. As wafer sizes increase and feature sizes shrink, equipment and facilities costs rise significantly. Advanced factory-level process control is now recognized as a vital technology for achieving the device yield and productivity levels required to compete effectively, but its deployment has been limited to date by the lack of sufficient integration technology and standards.
Important characteristics in factory-level process controls should include:                scalability—can be applied to a single process tool and its dedicated metrology or across multiple interdependent process areas; the system can be installed on a single computer, or spread across a distributed platform of multiple machines, depending on the performance and reliability requirements;        compatibility with existing systems—designed and validated to work with today's manufacturing systems;        flexibility—control functions are not “hard-wired” into the architecture, but rather embodied in software and control application “plug-ins”; and        standards-based for easy portability.Still other factors may become important, and perhaps even predominate, depending on the context of a particular implementation.        
The failure of current process controls to adopt these characteristics produces numerous inefficiencies. Traditional process control has been what is known as statistical process control (“SPC”). SPC usually detects only two types of process problems. An abrupt change in process behavior or incoming material will be flagged when one or two SPC data points fall near or outside the SPC control limits. A shift in a process will be detected by SPC rules that look for four out of five points more than one sigma away from the process mean, or eight consecutive points all on one side of the process mean. SPC systems typically provide for corrective actions to be defined for each of their rules. Abrupt changes will elicit an indication that there is a problem, prompting for manual identification and resolution.
The present invention is directed to resolving one or all of the problems mentioned above.